G.V. Bogatirova, Ch.V. Felde, P.V. Polyanskii Referenceless testing of vortex optical beams.// Optica Applicata. - 2003. - Vol. 33, No 4. - Р.536-548.

A new simple technique for determining the phase handedness (clockwise or counterclockwise) of vortex optical beams, which does not require implementation of an interferometric arrangement, is introduced. It is shown that both the phase handedness and the modulus of an azimuthal mode index of the beam can be directly and unambiguously determined on the basis of bending of interference fringes in a “strip” Young’s interference experiment. The initial results are obtained by simulation, partially demonstrated and discussed. Applicability of the proposed technique to testing elementary and complex vortex-bearing optical beams and fields is discussed.